| 摘要 |
PROBLEM TO BE SOLVED: To recover an acid of a high concentration and a hydroxide of metal from an acid waste liquid containing a metal salt by combining a diffusion dialysis process, mechanical separation process, and electrodialysis process in which a specific bipolar membrane and anion, cation-exchange membranes are used. SOLUTION: An acid waste liquid 9 containing a mineral acid and a metal salt thereof is supplied to a dialysis chamber 1 of a diffusion dialysis device I, while a dilute acid is supplied to a diffusion chamber 2 to efficiently recover the acid from the acid waste liquid. A deacidified liquid 10 obtained by this process in the chamber 1 is fed to a neutralization settling separation device II, where the liquid neutralized with an alkaline liquid 12 and the metal salt in the liquid is settled as a hydroxide, which is taken out as sludge or slurry 13. On the other hand, a neutralized, filtered liquid 14 is passed through a chelate resin column 15, as required, depending on the content of salt having low solubility and fed to an ion-exchange membrane eletrodialysis device III to selectively dialyze ions of the liquid 14 through cation- exchange membranes and anion-exchange membranes so that acid of high concentration and alkali of high concentration are obtained respectively in an acid generating chamber 7 and base chamber 8 through a bipolar membrane having a fixed ion concentration of a cation-exchange resin part equal to or larger than 10N. |
